Gyratory sifter



April 27, 1954 Filed Dec. 5, 1950 H. E., TEMPLE GYRATORY SIFTER 4 Sheets-Sheet l /V//PAM E. 7Z'MPLE April 27, 1954 H. E. TEMPLE GYRATORY SIFTVER 4 Sheets-Sheet 2 Filed Dec. 5, 1950 April 27, 1954` H, E, TEMPLE 2,676,706

GYRATORY SIFTER I Filed Dec. 5, 1950 LLSheets-Sheer. 5 v

VvE/vrom- @a K www@ H. E. TEMPLE GYRATORY SIFTER April 27, 1954 4 Sheets-Sheet 4 Fj led Dec. 5, 1950 Patented Apr. 27, 1954 GYRATORY SIFTER Hiram E. Temple, San Gabriel, Calif., assigner to .Read .Standard Corporation, a corporation of Delaware vApplication'December 5, 1950, Serial No. 199,320

14 Claims.

The present invention relates to a gyratory sifter and will be considered herein in connection with flour sifting for purposes o'f illustration.

In general, a primary object of the present invention is to provide a gyratory sifter which .includes a sifting structure `movable in an orbit about a substantially vertical axis of gyration.

Another object is to kprovide crank .means carried by and rotatable relative to a suitable Ysupporting structure for .moving the sifting structure in an orbit -of .constant diameter about a Asubstantially vertical vaxis'of gyration, and which includes means connected to the supporting Vstructure and to the sifting structure for substantially preventing rotation of the sifting structure relative to the` supporting structure as it moves .in its orbit about the axis of :gyraticn An important object is to provide a gyratory lsifter of the foregoing character wherein the sifting vstructure is 'counterbalanced so as to prevent excessive `vibration of the sifter and to prevent excessive transmission of excessive vibration to .the building or other structure in which the sifter -is installed.

Another important object-of the .invention is to provide a sifting structure .comprising a 'series of vsifting units which are vstacked one .upon the other and into which unsifted flour is introduced in sequence. In other Words, another important object of the invention is to provide a sifting structure having such a series of sifting units in which unsifted :flour discharged by any Aof the -sifting'units in the series, .excepting the last sift- `ing 'unit in the series, is 'introduced into the next sifting 'unit .in the series. With this :construction, the maximum percentage of ifi-our particles `which are :small enough to :pass through the sifting units .is recovered, which is an important ifeature oi the invention.

Another object yis `t-o yprovide a Vsifting structure ,in which the sifting units Iinclude ysubstantially horizontal lannular sifting elements which :are pervious to flour particles not exceeding -a predetermined siZe, but impervious to .our .particles exceeding this predetermined size and adapted 'to discharge such oversize .particles over their 4outer 'peripheries upon orbital movement of the sifting structure "ab'out'its axis of gyration.

Another important object of the invention is to provide a sifting structure Yfor a gyratory siiter wherein the'jparticles passing through the sifting elementsof the sifting vunits converge "toward a central outlet passagemeans, and wherein the particles discharged over the outer peripheries of the sifting element-s 'descend'in an annular,

zigzag path.

Still `another Aobject is to provide discharge conveyor means in each sifting unit above the lowermost for conveying oversize particles discharged over the outer periphery of its sifting element inwardly and downwardly onto the sifting element -of the sifting unit therebeneath. A related object is to provide a sifting structure wherein the discharge conveyor means of each sifting unit comprises an inwardly and downwardly sloping funnel carried lby an annular housing element of such sifting unit, the sifting element of such sifting unit also being carried by the annular housing element thereof. Thus, such discharge funnels convey the oversize particles discharged by the sifting elements of 'the sifting units above the .lowermost sifting unit onto the sifting elements of the sifting units therebeneath, respectively, whereby a maximum percentage of the siftable particles is recovered.

Another object is to provide a sifting structure which includes a central outlet passage means encircled by the annular sifting units, each sifting unit including an outlet conveyor means below the sifting velement thereof for conveying particles passing through the sifting element thereof inwardly and vdownwardly into such central outlet passage means. A related object is to provide each sifting unit with an outlet conveyor means having the form of a funnel with a central opening which registers with the cen,- tral outlet passage means.

.Another object is to provide each sifting unit with means for vibrating its sifting element to .facilitate passage of `the flour particles therethrough. Preferably, the vibrating means of each sifting unit includes a 4plurality of balls adapted to imp'inge `on .the sifting element thereof.

While the central outlet passage means referred to above may be a .single outlet passage into which the particles passing through all of the sifting elements are conveyed, it will be understood that the central outlet passage means .may also include a plurality of outlet passages, such as concentric Aoutlet passages, into which the particles passing through different ones of the sifting element-s are respectively conveyed, such an arrangement having utility where it is desired to separate the hour into different grades according `to particle size.

Still another .object of the present invention is to provide such a .siftingstructure having a base beneath the stack of sifting units and having a cover above such stack, the cover being provided with an inlet means for the flour to be sifted and the 'base being provided with an outlet means for the sifted flour and a'discharge means for the flour discharged or rejected by the sifting units. The flour discharged or rejected may consist of lumps of flour, or particles of flour too coarse to pass through the sifting elements.

Still another important object of the present invention is to provide a sifting structure of this character wherein the cover, the sifting units and the base are all readily separable for cleaning.

Another object in connection with the foregoing is to provide a sifting structure wherein the sifting units are merely stacked on each other, the lowermost unit in the stack being seated on the base and the cover being seated on the uppermost unit in the stack. Thus, the various components of the sifting structure may be assembled and disassembled readily by merely stacking and unstacking them. With this construction, the entire sifting structure may be disassembled for cleaning, or for other purposes, in a matter of a very few minutes, which is an important feature.

Another object is to provide interlocking means on the base, sifting units and the cover for lmaintaining these components of the sifter in axial alignment, a related object being to provide readily releasable means for securing such components together.

Another object is to provide a construction wherein the outlet funnels incorporated in the sifting units above the lowermost unit in the stack engage the respective sifting units therebeneath and are formed of resilient sheet material in a state of upward deformation so that the inherent resilience of such funnels biases them into positive engagement with the sifting units therebeneath. With this construction, no seals between the outlet funnels and the sifting units therebeneath are required, which is an important feature of the invention.

The foregoing objects and advantages of the present invention, together with various other objects and advantages which will become apparent, may be attained with the exemplary embodiments of the invention which are described in detail hereinafter. Referring to the accompanying drawings:

Fig. 1 is an elevation, partially in Vertical section, of a gyratory sifter which embodies the invention;

Fig. 2 is a horizontal section taken along the broken line 2 2 of Fig. 1;

Fig. 3 is a fragmentary vertical section taken along the broken line 3 3 of Fig. 2;

Fig. a is a fragmentary plan view of part of one of a stack of sifting units incorporated in the sifter of the invention;

Figs. 5 and 6 are fragmentary vertical sections taken along the broken lines 5 5 and 6 6, respectively, of Fig. 4, Fig. 6 being on an enlarged scale; l

Fig. 7 is a horizontal section taken along the broken line 1 1 of Fig. 1; and

Fig. 8 is an enlarged vertical section taken along the broken line 8 8 of Fig. 7.

Referring particularly to Fig. 1 of the drawings, the gyratory sifter of the invention includes a sifting structure, indicated` generally by the numeral I I, which is carried by any suitable supporting structure, indicated generally by the numeral I2, for orbital movement relative to the supporting structure about an axis of gyration A A. In the particular construction illustrated, the gyratory sifter includes main crank means 13 for gyrating the sifting structure II in its orbit about the axis of gyration A A, and includes restraining means, exemplied as auxiliary crank means I4, for substantially preventing rotation of the sifting structure relative to the supporting structure I2 upon orbital movement of the sifting structure about the axis of gyration. In order to minimize the transmission of vibration to the building or other structure in which the gyratory sifter is installed, the sifter is provided with means I5 for counterbalancing the sifting structure II. The main crank means I3, which is rotatable about the axis of gyration A A to produce orbital movement of the sifting structure I I about such axis, is adapted to be driven by an electric motor I6 mounted on the supporting structure I2 in the particular construction illustrated.

As a matter of convenience, the components of the gyratory sifter which are associated with the production of orbital movement of the sifting structure II about the axis of gyration A A and with the counterbalancing thereof will be considered in detail before considering the details of the sifting structure I I, such components having utility with other sifting structures than the particular sifting structure I I described hereinafter, as disclosed in the aforementioned copending application, for example.

Referring particularly to Figs. 1 and '1, the supporting structure I2, in the particular construction illustrated, is of generally triangular configuration and includes three tubular standards 2| interconnected by upper and lower horizontal braces 22 and 23 welded or otherwise secured thereto. The standards 2I are provided at their lower ends with annular flanges 24 for use in bolting or otherwise securing the supporting structure I2 to a iioor, or the like. Spanning the space between and welded or otherwise secured to two of the upper horizontal braces 22 is an upper angle 21, and spanning the space between and welded or otherwise connected to the corresponding two lower horizontal braces 23 is a lower angle 28 parallel to and disposed directly below the upper angle 21. Bolted or otherwise secured to the upper and lower angles 21 and 28 are upper and lower bearings 29 and 30, respectively, which are coaxial with the axis of gyration A A. Disposed in the bearings 29 and 30, which are preferably thrust resisting, is a main crankshaft 3I which forms part of the main crank means I3 and the axis of which coincides with the axis of gyration A A. The main crankshaft 3| is adapted to be rotated about the axis of gyration A A by the motor I6 through a belt 32 trained around a pulley 33 secured to the main crankshaft and a pulley 34 secured to the shaft of the motor. The motor I6 is bolted or otherwise secured to a hanger 35 which is pivotally connected, by a pin 36, to upper and lower brackets 31 and 38, respectively, welded or otherwise connected to one of the upper horizontal braces 22 and one of the lower horizontal braces 23. As best illustrated in Fig. '1 of the drawings, the tension in the belt 32 may be regulated by means of an adjusting bolt 39 which is connected to the hanger 35 and to an angle 40 welded or otherwise connected to the same upper and lower horizontal braces to which the upper and lower brackets 31 and 38 are connected. The adjusting bolt 39 has nuts 4I threaded thereonto on opposite sides of one ange of the angle 4I) and, as will be apparent, by varying thepositions of these nuts on the adjusting bolt, the .hanger k35 with the motor I6 thereon maybe rotated about the axis of the pivot -pin 36 to adjust Ithe :belt tension.

The main crankshaft 3-I includes a flexible coupling-46 for absorbing differences in the speed lof the -motor 'I6 and the speed of 'gyration of the sifting structure II in its orbit about the vaxis Vof `gy-ration A-A. Connected to the upper ,endkof the flexible coupling 4B and forming part of lthe main crankshaft 31 is an eccentric li'Iv having a v.bore 48 therein the axis of which is lsubstantial-ly parallel to but `spaced from the axis `of gyration A--A of the sifting `structure I I. Disposed in the bore 48 is the lower end of an elongated crank pin 49, the lower end of the crank pin beingrigidly connected lto the eccentric .41, as by a key 510. The axis of Athe crank pin 4.9 coincides Ywith .the central axis, or axis of symmetry, of the sifting .structure II .in the particular construction illustrated, the axis ofthe sifting structure being des- `ignated as B-B. Encircling the crank :pin 4.9 .and rotatably connected thereto by `upper and vlower bearings 5I and 52, which are preferably 'thrust resisting, is a sleeve 53 to which the sifting structure I I is connected, as will be discussed in more detail hereinafter.

As will be apparent, when the main crankshaft 13| is rotated about the axis of gyration A--A by `the motor I6, the crank pin 49 moves in an `orbit .about the axis of gyration A--A, the diameter of such orbit being determined by the distance between the axes A-A and ZB-B. Thus, the crank pin 49 moves .the sifting structure II about the axis of gyration `A--A in the same orbit to pro- -ducethe desired `orbital movement of the sifting gstructure. `'I'he bearings 5I and 52 permit the crank pin 49 to rotate relative to the sifting .structure II as the main crankshaft '3| is rotated, thus permitting the sifting structure I.I to remainsstationary relative to the supporting structuren except for its orbital movement relative thereto 'about theaxis of gyration A-A. `In other words, the structure thus far .described permits gyration A.of the sifting structure .II relative to the ysupporting ystructure I2 about the axis of gyra-tion A-A, but does not produce `rotation of the sifting structure relative tothe supporting structure except for the effect of friction in the bearings 5-I and 52.

The Veect of such friction is overcome v'by the restraining' action of the aforementioned 'auxi'liary crank means I. In the particular construction illustrated, the latter includes three auxiliary cranks or crankshafts 56 respectively .carried by the standards "ZI, one of the auxiliary crankshafts 5d being illustrated in detail in Fig. 8 .of the drawings. Referring thereto, each crankshaft 5'8 is carried by bearings '51, which are preferably thrust resisting. These `bearings are pressed into a tubular tting 58, which, in turn, is telescoped into vthe upper end of one of 'the standards 2I A fia-nge 59 on the,` fitting 5'8 seats on and is preferably bolted to ya flange 60 at the upper end of such standard. crankshaft 55 is provided with an offset crank pin lEI, the offset of the crank pin lSI being equal to the distance between vthe axes A-A andB--B Each crank pin Si is rotatably connected to `a fitting 62 by a bearing E3, which is also preferably thrust resisting. `The ttings 62 are bolted, or otherwise secured, to the sifting structure 'I I, as best'shown in Figure l Aof the drawings.

As will be apparent, .the `sifting 'structure II is supported by the .main .crankshaft 3.I :and the Each auxiliary .f

auxiliary .crankshafts r56, which Ais the reason for employing bearings of the thrust resisting type, .as hereinbefore indicated. If desired, the bearings shown may be Ysupplemented by conventional thrust bearings, not shown.

Thus, yas the sifting structure II is moved orbitally about its axis of gyration A-A upon rotation of the main crankshaft 3i, it is prevented from rotating relative to the supporting structure I2 by the auxiliary crankshafts 5t, except for a .slight rotary oscillation resulting from rotation of the auxiliary crankshafts.

As previously indicated, the sifting structure is counterbalanced to prevent excessive vibration transmission to a floor or other structure on which the supporting structure I2 is mounted, the counterbalancing means I5 counterbalancing ttheqsifting structure II at both its upper and lower ends, which is an important feature of the invention. More particularly, the counterbal- ,ancing means I5 includes two substantially equal 'counterweig-hts '6 5 and =6`I respectively located at the lower and upper ends of the crank pin 49. The .counterweight 66 is carried by an arm 68 7 which 'is rig-idly connected to the eccentric 47, las

'by being .formed integrally therewith. The upper `cou-nterweight 6l is carried by an arm S9 which is rigidly connected to a hub lil, .as by being formed integrally therewith. The upper end of :the crankpin i9 is inserted into a bore in the hub .79, the latter being fixed on the vcran-k pin, as by -a key ll. The `counterw.eights 66 and 61 are vertically aligned and, as best shown in Fig. 7 of :the drawings, are disposed diametrically opposite `the crank pin 49 with respect to the axis of Igyration A--A, ythe counterweights being maintained in vertical alignment 'because of the fixed `connections 'between the .crank pin 49 and the veccentric 4.1 and `between the crank pin and the Yhub lil. Thus, it'will be apparent that, by counterbalanlcing the sifting Astructure I I at both the upper and lower ends thereof in this manner, vibration of the entire gyra-tory sifter is minimized. y'Other counterbalancing means are disfeicsed in the aforementioned yco-pending applivlcation.

'Turning now 'to -a consideration of the details of the sitting structure I I, and referring particularily to Fig. 1 `of the drawings, the sifting strucs'tu-re Aisof cylindrical 'configuration in the particu- 7lar construction illustrated and includes a base fi15,.a,stack of sifting vunits 'E6 and a cover ll, the .stack of sifting units being seated on the base .andthe coverbei-ngsseated on Athe stack of sifting iunits. With Athe exception 7of the lowermost sifting'unit in the stack, each sifting unit is seated on the one therebeneath, the lowerinost sifting runit'lneingrseaited on'the base i 5.

The base 'fl-"5 includes a vcentral hub 3i which receives the lower end of the sleeve 53 encircling lthe crank pin 49. 'The base l5 also includes an .annu-lar lrim :82 which is connected to the hub 8l :adisc Jor web '83, thedisc 83 sloping generally outwardly and downwardly from the hub to the riin, and being :imperforate except as hereinafter vindicated. V-In the :particular construction illus- 'trated, ithefhub 8'-I,fthe rim 82 and the disc 83 take :the form of a single casting.

The fittings 52 associated with the auxiliary cranks-baits 55 are connected to the vbase 'l5 of fthe sifting structure il, as by cap screws 8d. As fbestshown in Fig. il 'of thevdrawings, the base "I5 inay he :provided with depending bosses into w 'ch the screws 19E are threaded. Thus, the sitting vstru'etui-'rie Il is supported `by the standards 2| through the auxiliary crankshafts 56 and the elements associated therewith.

Each sifting unit 'i6 includes an annular housing element S2 which is illustrated as being of the same diameter as the annular rim S2 of the base T5. Each housing element 88 is provided on its upper edge with an annular, upwardly eX- tending tongue t@ which is received in a complementary groove in the lower edge of the housing element thereabove. lThe annular rim 82 is provided with a similar tongue Qi! which is received by a complementary groove in the lower edge of the lowermost housing element 88. rThe tongue 8S on the upper edge of the uppermosthousing element 323 in the stack its into a complementary groove in the lower edge of an. annular rim 9| of the cover 11.

Thus, as will be apparent, when the sifting units 16 and the cover 11 are stacked on the base 15 in the order illustrated in Fig. l of the draw- 1 ings, the tcngue-andgroove connections between the base 15 and the lowermost housing element 06, between adjacent housing elements, and between the uppermost housing element and the cover serve to retain the entire assembly in axial alignment with respect to the axis B-B of the sifting structure H. Consequently, the sifting structure may be assembled readily by merely stacking the sifting units and the cover on the base 15, as will be apparent. In order to secure the components of the sifting structure tgether, straps 82 adapted to hook over the lower edge of the annular rim 82 of the base 15 are provided, such straps being tensionable by means of toggle-type locking devices 9% suitably connected to the rim 9| of the cover 11. As will be apparent, the length of the straps 02 depends on the number of sifting units 16 employed, the number of sifting units being variable merely by varying the length of the crank pin 119 and by correspondingly varying the length of the sleeve 53.

In addition to the rim 9| the cover 11 includes a central hub S6 which receives the upper end or" the sleeve 53 encircling the crank pin 49, the rim 0| being connected to the hub 66 by a web or disc 01. In the particular construction illustrated, the rim Si, the hub 96 and the web or disc 91 of the cover 11 are formed as a single casting. The disc 61 of the cover is provided with a central recess or well 98 which receives the counterweight El' and in which this counterweight is rotatable, the well 08 being extended upwardly by an annular ange 99 illustrated as formed integrally with the .disc 91. A cap |00 telescopes over the annular ilange 96 to completely enclose the counterweight 61.

The cover 11 is provided with an inlet means for the ilour or other material to be sifted, such inlet means comprising inlet openings encircled by upwardly extending annular flanges H36 to which ilexible conduits, not shown, for delivering the flour into the sifting structure H may be connected in any suitable manner. Below each inlet opening |05 is a baille or diffuser |08 for distributing the flour owing through such inlet opening over the surface of the uppermost sifting unit 16, the baffles |08 being bolted or otherwise secured to the cover 11.

Turning now to a more detailed consideration of the sifting units 16, and referring particularly to Fig. l of the drawings, the sifting units above the lowermost unit in the stack are identical and the lowermost unit is similar thereto. Consequently, only the lowermost sifting unit 16 and one of the sifting units thereabove will be considered in detail and the lowermost sifting unit will be described by pointing out the diierences between it and each sifting unit thereabove.

Connected to the annular housing element 38 of each sifting unit 16 above the lowermost unit in the stack, as by being formed integrally therewith, is a downwardly converging conical wall or funnel which, as will be described in more detail hereinafter, serves as a discharge conveyor means for conveying oversize particles discharged by such sifting unit inwardly and downwardly onto the sifting unit therebeneath. The annular housing element 88 of the lowermost sifting unit 16 in the stack is provided with a similar conical wall Hla, the only difference being that the central discharge opening in the conical wall Ia is of larger diameter than the central openings in the conical walls or discharge funnels |H. Each of the discharge funnels |H and the conical wall Hla is provided adjacent its periphery with a plurality of circumferentially spaced, upwardly extending bosses H2 each of which is provided with a central, upwardly eX- tending pin H3. Seated on the bosses H2 of each sifting unit 16 and positioned by the pins I IS associated with such bosses is a sifting means H5, the pins H3 extending through suitable openings in the sifting means. All of the sifting means H5, including the sifting means of the lowermost sifting unit 16 are identical so that only one of them will be considered in detail.

Each sifting means H5, as best shown in Figs. 4 to 6 of the drawings, is of annular conguration and includes a spider or spider means H6 having a central annular hub H1 and an angleshaped rim H8 connected to the hub by spokes i9. Each spider I0 also includes arcuate braces |20 between adjacent spokes H9, each arcuate brace dividing the area between a pair of spokes into inner and outer compartments |2| and |22. As will be discussed in more detail hereinafter, the central opening through the annular hub of each sifting means H5 below the sifting means of the uppermost sifting unit 16 serves as an outlet opening for flour, or other material sifted. by the sifting means thereabove. It will be noted that, referring for the moment to Fig. l of the drawings, the central openings through the annular hubs H1 are all axially aligned so that such central openings serve as a central outlet passage means |23 for the sifted ilour, or other material, as will be further discussed hereinafter.

The sifting means H5 of each sifting unit le includes an annular sifting element |25, which may be formed of a fabric, such as silk, or which may be formed of wire screen, for example. The inner periphery of the sifting element 25 of each sifting means H5 is clamped between the annular hub H1 of the corresponding spider HS and an annular collar |25 which is secured to such annular hub in any suitable manner. as by screws |21. The outer periphery of each sifting element |25 is bent downwardly over the rim I8 of its spider I6 and is secured by a circumferential band or hoop |20, the ends of the latter boing connected together by a screw |29, Fig. l. Preferably, as best shown in Fig. 6, the outer peripheral surface of the rim H8 of each spider H6 is provided with an annular groove i3d to receive the outer periphery of the corresponding sitin. element |25 and the retaining hoop thereby providing a substantially iiush construction. Thus, the sifting element |25 o1" each sifting means H5 is retained at its inner and outer pe #tenerme 9 1 ripheries., and is supported,intermediate-its inner and outer peripheries by Ithe-spokes. I9.` andthe arcuate bracesr |20.

In the. event that a. kfabric such :as silk is `employed for the sifting elements |25, it is desirable to provide means for vibrating. such, si'f1tng ele.- ments to some extent during voperation .of the gyratory sifter so as to facilitate passage ofthe ilour, or other material, therethrough.` Such'vibrating means may take the form of `balls Y|33 disposed` in the compartments |-2| and |22 provided by the spiders H6. y ated with each sifting means ||5 are retained ,by a coarse screen |134 which is secured to `the annular hub |f|1 and the rim ||f 8 of the corresponding spider ||6 adjacent its inner and outer peripheries, respectively. Each screen |34 issecu-red at its inner periphery by a ring |135 attached to the annular hub ||1 of the corresponding spider H6 by screws |-36or tl'1eflilce, `the inner periphery of each. screen thus being clamped between the corresponding hub H1 and `the corresponding ring |35. Similarly, the outer periphery of each screen |34 is clamped between the rim ||8 of the corresponding spider ||6 and a ring |31, the ring |31 being secured by screws |38 or the like.. As will be apparent, the Iballs |33 tend -to bounce somewhat during orbital movement of the sifting structure VI as they roll over the relatively ycoarse supporting screens |34. Thus, the balls strike the sifting elements |25 to vibrate them and facilitate passage of flour, `or other material.

In theevent that wire screens, for example, are employed for .the sifting elements |25, .particuf larly Where coarser grades of flour are being sifted, the balls |33 may be omitted, if desired. With such a construction, the retaining screens |34 for the balls and the rings |35 and |31 for retaining such screens may also be omitted.

Ars best shown in Fig. l of the drawings, the outside diameter of each annular sifting means ||5 i's less than the inside diameter of the cor-.- responding annular housing element 88 so as to provide therebetween an annular discharge pas,-Y sage means |4| through which any unsifted our, or other material, discharged over theo-liter periphery of the corresponding sifting element |25 may now onto the discharge funnel therehe neath. Each discharge funnel thus conveys the oversize particles discharged over the outer peripheries of the sifting elements |25 inwardly and downwardly onto the respective sifting elements therebeneath, the diameter of the central openings through the discharge funnels exceeding the inner diameters of the sifting 'ele. ments but being less than the outer diameters thereof so that the flour conveyed by the funnels is deposited on the sifting elements therebe-y neath intermediate the inner and outer peripheries thereof.

Each sifting unit 16, with the exception of the lowermost unit in the stack, includes a downwardly converging, conical wall or outlet funnel |42 which serves as an outlet conveyor means for conveying the flour, or other material, siited through the corresponding sifting element 25 inwardly and downwardly into the aforementioned central outlet passage means |23, the latter being defined by the annular hubs |1 of the sifting means H5, as previously discussed. As best shown in Figs. 5 and 6 of the drawings, theouter periphery of each outlet funnel |42 isi clamped between the outer ring |31 of the corresponding: sifting means |5 vand the outer periphery ofthe The balls |33 associ.-

retaining-:screen |L34; for the balls |33, so that :the outlet funnel 4|42 associated with keach sifting means :H5 may be. installed .and removed with suchfsi-fting means. However, connecting the outlet yf ,unrflels -|42 :to the sifting means ||.5 in this .manner isnot necessary and ther outlet funnels vmay merely be seated on ythe supporting bosses |,|:j2 Vbeneath the sifting means ||5 so as to be' installableand removable separately, if desired. This latter construction is particularly desirable i-na sitting structure which must be cleaned frequently for Asanitation purposes. As will-be apparent, the outlet funnels are separate from the-*sifting means ||.5, and if the retaining screens` |34 for the balls |33 are not employed, the flower surface of each sifting element |215 is exposed for ready cleaning upon removal of the sifting means of which it forms a part.

.Each outlet funnel |42 is provided with a downwardly extending annular flange |44 which encircles the central opening therethrough and which telescopes vinto the collar |26 on the annular hub ||1 of the spider ||6 therebeneath, as best shown in Fig. 1 of the drawings. Preferably, the outlet yfunnels |42 are formed of resilient sheet material, such as sheet metal, and are .in a state of upward deformation when the sifting structure isv assembledr so that the inherentrresilience of the outlet funnels |42 seats them firmly on the collars |26 therebeneath, the collars preferably being beveled to provide relatively large areas of contact between them and the outlet funnels. In other words, the vertical distance between the outer periphery of each outlet funnel |42 and the inner periphery thereof is Vnormally less than the spacing between the sifting means ||5 so that the funnels |42 are sprung upwardly upon assembly of the sifting structure to seat the funnels rmly on the collars |26. Thus, no seals are necessary between the outlet funnels |142 and the collars |26, which is an important feature.

It will be noted that the sifting means |5 and the' outlet funnels. |42 merely seat on the sup porting bosses ||2 and are not secured to the annular housing elements 88 against upward movement. As will be apparent, the sifting means |.|`5A of the lowermost sifting unit 16 is retained by the outlet funnel |42 of the sifting unitthereabove. Similarly, the sifting means H5 and the outlet funnel |42 of each sifting unit 16 above the lowermost is retained by the outlet funnel of the sifting unit thereabove, excepting the uppermost sifting unit in the stack. The outlet funnel I 42 and the sifting means I5 of the latter are secured against upward movement by telescoping the collar |26 of such sifting means into an annular collar |45 which extends downwardly from and is illustrated as formed integrally with the cover 11, The collar I 45 provides an internal annular shoulder |46 which serves as a seat for the collar |26 of the uppermost sifting means. Thus, when the cover 11 is` installed after the sifting units 16 have been stacked, the cover automatically secures the various sifting means ||5 and outlet funnels |42 against upward movement in the manner hereinbefore discussed. Also, as the various compcnents are assembled, the outlet funnels' 42 vare automatically sprung upwardly to provide the desired seals between the outlet funnels and the respective sifting means therebeneath.

As best shown in Figs. l to 3 of the drawings, the area between the hub 8| of the base 15'v and the rim 82 thereof is divided into an inner. outlet compartment for sifted flour and an outer, discharge compartment |52 for flour particles too large to pass through the sifting elements |25, the separation between the outlet and discharge compartments |5| and |52 being provided by a circular wall |53, illustrated as formed integrally with the disc or web 83 of the base '15. That portion of the disc or web 83 which defines the lower wall of the inner, outlet compartment |5| is provided with arcuate outlet channels |54 which slope downwardly from high points |55 to outlet openings |55. The directions of downward slope of the outlet channels |54 from the high points |55 to the outlet openings |56 are indicated by arrows |51. Encircling each outlet opening |56 and extending downwardly is an annular ange |58 to which a flexible conduit |55 is connected in any suitable manner, as by being telescoped thereover. The flexible conduits |59 leading from the outlet openings |55 are connected to a common outlet conduit |65, as shown in Fig. 1.

rlhus, the outlet channels |54, the outlet openings |55, the i'iexible conduits |59, and the outlet conduit |55 form an outlet means for sifted flour. It will be noted that the sifted ilour conveyed into the central outlet passage means |23 by each of the sifting units 16 above the lowermost sifting unit drops onto that portion of the disc or web 83 of the base 15 which forms the bottom of the inner, outlet compartment |5| and nnds its way into the arcuate outlet channels ld, the sifted our thereafter descending along such channels toward the outlet openings |56. No outlet funnel |42 is provided for the lowermost sifting unit "i6 in the stack, the lour passing through the sifting element |25 thereof falling directly onto the bottom of the outlet compartment |5|.

That portion of the disc or web 83 of the base 75 which denes the'bottom of the outer, discharge compartment |52 is provided with arcuate channels |55 which slope downwardly, as indicated by the arrows |66, from a high point |51 to a discharge opening |58, the channels |65 and the opening |58 providing a discharge means for particles too large to pass through any of the sifting elements |25. The discharge opening |68 is encircled by a downwardly extending, annular flange |59 to which a nexible discharge conduit |15, Fig. 3, may be connected in any suitable manner.

It will be noted that the diameter of the central opening through the conical wal1|||a of the lowermost sifting unit 16 is greater than that of the circumferential wall |53 which divides the base into the outlet and discharge compartments l5 and |52 so that any flour particles discharged over the outer periphery of the lowermost sifting means ||5 fall downwardly into the discharge compartment |52. Thus, the principal function of the conical wall |||a is merely to carry the bosses ||2 for supporting the lowermost sifting means ||5. As previously pointed out, the conical walls or discharge funnels are provided with central openings of a diameter considerably less than that of the central opening through the wall Illa, the conical walls or discharge funnels serving to convey oversize particles discharged by the sifting means ||5 above the lowermost sifting means inwardly and downwardly onto the sifting means therebeneath, respectively. I

It will be noted that while the sifting structure has been illustrated as provided with a single central outlet passage means |23 into which the outlet funnels |42 of all of the sifting units above the lowermost discharge, the sifting structure may be provided with a plurality of central outlet passages, one or more of the outlet unnels |42 discharging into each of such passages. Such a construction would have particular utility in flour mills for separation of the flour particles into a plurality of grades according to particle size.

Considering the operation of the gyratory siiter of the invention, when the motor i5 is energized, the main crankshaft 3| is rotated about the axis of gyration A--A to move the sifting structure in an orbit about the axis of gyration. At the same time, the auxiliary crankshafts 55, while substantially preventing rotation of the sifting structure li relative to the supporting structure i2 about the axis B-B of the sifting structure, do produce a rotary oscillation of the sifting structure about the axis B-B through a limited angle. As previously discussed, the sifting structure is counterbalanced to avoid developing excessive Vibration.

The foregoing compound movement of the sifting structure i, i. e., the orbital movement thereoi about the axis of gyration A-A and the rotary oscillation thereof about the axis B-B, agitates flour, or other material, on the sifting elements |25 to facilitate passage of siftable particles through the siting element, such agitation being enhanced by the balls |33 when employed. As previously discussed, the flour, or other material, to be sifted is introduced into the sifting unit through the inlet openings |65 and is deposited i'lr'st on the sifting element |25 of the uppermost sifting unit "l5, being diffused or spread by the bales |58 to insure even distribution and to prevent damage to the uppermost sifting element. The particles passing through the uppermost sifting element |25 are conveyed to the central outlet passage means |23 by the corresponding outlet funnel |42 and descend through the central outlet passage means into the outlet compartment |5 thereafter descending along the arcuate outlet channels |54 to the outlet openings |56. Any particles or lumps which fail to pass through the uppermost sifting element |25 move outwardly as a result of the aforementioned compound movement of the sifting structure and are discharged over the outer periphery thereof, passing through the uppermost discharge passage means |5| and dropping onto the uppermost discharge funnel The latter conveys such particles and/or lumps inwardly and downwardly and deposits them approximately midway between the inner and outer peripheries of the second annular sifting element |25 in the stack. Additional particles pass through the second sifting element in the series and are conveyed inwardly and downwardly to the central outlet passage means |23, through which they descend in the manner hereinbefore described. Again, any particles failing to pass through the second sifting element |25 are clischarged over its periphery and are conveyed onto the third sifting element by the second discharge funnel This process is repeated until the unsifted particles have been discharged over the outer periphery of the lowermost sifting element |25 in the stack, such particles falling into the .discharge compartment |52 and then into the i 13 annular discharge channel |f6`5`,- whi'chl conveys them to' the discharge opening |68'.

Thus, the iiour sifted by each sifting element |25 above the lowermost is conveyed inwardly to the central outlet passage means |253, the flour sifted by the lowermost sifting element falling directly into the outlet compartment IVE-I'.

through successive sifting elements |25 descend through-the sifting structure I in zigzag fashion until they either pass through one of the sifting elements, or are ultimately discharged over the outer periphery of the la-st sifting element in'- the series and into the discharge compartment |52'. With this construction, a maximum percentage of the siftable flour is recovered, which is animportant feature.V

As will be apparent, the sifting structure Il' may be disassembled for cleaning very readily. In disassembling the sifting structure Il', the first step is to remove the cap covering the counterweight well 98. Subsequently, the upper counterweight t1 may be disengaged from the crank pin 49 and the cover 11 may then be removed after releasing the toggle-type locking devices' e3. Thereafter, the sifting units '|16 may be removed in sequence. Also, the sifting means H5 and the outlet funnel? |42 of each sifting unit' may be separated' from the housing element 88 thereof, either as a' unit, or separately, depending upon` whether the outlet funnel is attached to the sifting means, or is separable therefrom, as previously discussed. Thus, all of the elements of the sifting structure are exposedto facilitate cleaning. As will be apparent, the structure may be reassembled by reversing the foregoing procedure.

It will be understood that the number of sifting units 'I6 employed may vary. For example, if it is not essential` that tiny lumps of flour be broken up into their individual particles, al few sifting units T6 employing relatively coarse sifting elements |25 may be employed'. On the other hand, if it is desired to breakup such tiny lumps to produce an extremely line sifted product, a larger number of sifting units 16 employing finer sifting elements' |25 may be employed. As will be apparent,- crank' pins and encircling sleeves 53 of different lengths may be provided for different numbers of sifting units.

The gyratory sifterV of the invention iscapable of sifting flour in large volume and. at a high rate. Moreover, this is accomplished with a minimum of vibration transmission to the building or other structure in which the sift'er is used..

It will be understood that various changes, substitutions and mo'dications may be incorporated in the exemplary embodiments hereinbefore disclosed without departing from the'spirit of the invention.` For example', the sifting structure may be of coniigurations other' than cylindrical, and the central axis B`B thereof need not coincide with the axis of the crank pin 49, but may be spaced therefrom.

The invention is defined by the following claims:

1. In a gyratory sifter, thel combinationof: a supporting structure; a sifting structure mounted on said supporting structure for orbital movement about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, said sifting structure being provided with a series of substantially horizontal, `vertically spaced, annular, sifting elements which Onthe other hand, particles which do not pass' areA substantiallyV symmetrical about said central# axis and each of which is pervious to particles'. not exceeding a predetermined size but is impervious to particles' exceedingY said predetermined size and is adaptedv to discharge such particles over its outer periphery upon orbital movement' of said sifting structure about saidY axis of' gyration, said sifting structure further including means' for conveying particles passing through thesifting elements above the lowermost sifting element in said series inwardly and downwardly to a central opening in ther sifting element therebeneath', the central openings in saidl siftingel'ements communicating with each other to provide a central outlet passage means com` mon'- tol said sifting elements and extending vertically` along said central axis through all of said sifting elements; and means for moving said! sifting structurel in an orbit about said axis of gyra'tion.

2.k Ina gyratory sifter, the combination of: a supporting structure; a sifting structure mounted on'` said supporting structure for orbital movement about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, said sifting structure including a stack of substantially horizontal, annular sifting units each of which is substantially symmetrical about said central axis' and each of which provides a substantially horizontal, annular sifting element pervious. to particles not exceeding a predetermined size, but impervious to particles exceeding said predetermined size and adapted to discharge such particles over its outer periphery upon orbital movement of said sifting structure. about said axis of gyration, each of said siftingl units above the lowermost sifting unit in saidl stack including first conveyor means for conveying particles passing through the sifting element thereof inwardly and downwardly to a central. opening in the sifting unit therebeneath, the central openings in said sifting units communicating with each other to provide an unobstructed-central outlet passage means common tov saidsifting units and extending vertically along said central axis through all of said sifting units; and each of said sifting units above the lowermost sifting unit in said stack including second conveyor means for conveying particles discharged over the outer periphery of the sifting element thereof inwardly and downward-Y ly onto the sifting element of the sifting unit therebeneath; and means for producing orbital movement of said sifting structure about said axis' ofV gyration, including a crankshaft connected to said sifting structure and extending through said outlet passage means.

3; In a gyratory sitter, the combination of: a supporting structure; a sifting structurev mounted on said supporting structure for orbital movement about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, said sifting structureincluding a stack of substantially horizontal, annular, sifting units each of whichis substantially symmetrical about said central axis and each of which provides a substantially horizontal, annular, siftingv element pervious to particles not exceeding a predetermined size, but impervious to particles exceedingy said` predetermined size and adapted to discharge such particles Over its outer periphery upon orbital movement of said sifting structure about said axis of gyration, said sifting ysi'lructure further providing central outlet passage means encircled by said sifting units and adapted to receive particles passing through the shifting elements of at least the sifting units above the lowermost sifting unit in said stack, and said sifting structure still further providing a series of peripheral discharge passage means respectively encircling the sifting elements of said sifting units and adapted to receive particles discharged over the outer peripheries of the respective sifting elements, each of said sifting units above the lowermost sifting unit in said stack including outlet conveyor means for conveying particles passing through the sifting element thereof inwardly and downwardly to said central outlet passage means, and each of the sifting units above the lowermost sifting unit in said stack including discharge conveyor means for conveying particles passing through the peripheral discharge passage means encircling the sifting element of such sifting unit inwardly and downwardly onto the sifting element of the sifting unit therebeneath; and means for producing orbital movement of said sifting structure about said axis of gyration, including a crankshaft connected to said sifting structure and extending through said outlet passage means.

4. A gyratory sifter as defined in claim 3 wherein each of the sifting units in said stack above the lowermost sifting unit therein is carried by the sifting unit therebeneath and wherein the sifting units are separable from each other, said gyratory sifter including means for securing said sifting units together.

5. A gyratory sifter according to claim 3 wherein each of said outlet conveyor means includes a funnel having a central opening which registers with said central outlet passage means, and wherein each of said discharge conveyor means includes a funnel having a central opening larger than said central outlet passage means but smaller than said sifting elements.

6. In a sifting structure movable in an orbit about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a stack of substantially horizontal, annular, separable, sifting units each of which is substantially symmetrical about said central axis and each of which provides a substantially horizontal, annular sifting element pervious to particles not exceeding a predetermined size, but impervious to particles exceeding said predetermined size and adapted to discharge such oversize particles over its outer periphery upon orbital movement of said sifting structure about said axis of gyration, each of said sifting units above the lowermost sifting unit in said stack including outlet conveyor means for conveying particles passing through the sifting element thereof inwardly and downwardly toward a central opening in the sifting unit therebeneath, the central openings in said sifting units communicating with each other to provide a central outlet passage means common to said sifting units and extending vertically along said central axis through all of said sifting units, and each of said sifting units above the lowermost sifting unit in said stack including discharge conveyor means for conveying particles discharged over the outer periphery of the sifting element thereof inwardly and downwardly onto the sifting element of the sifting unit therebeneath; and means for releasably securing said separable sifting units together.

7. In a sifting structure movable in an orbit about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a stack of substantially horizontal, annular, sifting units each of which is substantially symmetrical about said central axis and each of which includes an annular housing element, each of said housing elements above the housing element of the lowermost sifting unit in said stack being seated on the housing element of the sifting unit therebeneath, the housing element of each of said sifting units carrying a substantially horizontal, annular sifting element pervious to particles not exceeding a predetermined size, but impervious to particles exceeding said predetermined size and adapted to discharge such oversize particles over its outer periphery upon orbital movement of said sifting structure about said axis of gyration, said sifting element of each of said sifting units being spaced inwardly from the housing element thereof to provide a peripheral discharge passage means for particles discharged over the outer periphey of such sifting element, central openings through said sifting units providing central outlet passage means encircled by said sifting units and adapted to receive particles passing through the sifting elements of at least the sifting units above the lowermost sifting unit in said stack, the housing element of each of said sifting units above the lowermost sifting unit in said stack further carrying a downwardly and inwardly sloping funnel below the sifting element thereof for conveying particles passing through the sifting element thereof inwardly and downwardly to said central outlet passage means; a cover seated on the housing element of the uppermost sifting unit in said stack and providing inlet means for the introduction of particles to be sifted into the uppermost sifting unit in said stack; a base on which the housing element of the lowermost sifting unit in said stack is seated, said base being provided with outlet means communicating with said central outlet passage means and being provided with discharge means communicating with said peripheral discharge passage means; and means for securing said base, said sifting units, and said cover together.

8. In a sifting structure movable in an orbit about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a stack of substantially horizontal, annular, sifting units each of which is substantially symmetrical about said central axis and each of which includes an annular housing element, each of said housing elements above the housing element of the lowermost sifting unit in said stack being seated on the housing element of the sifting unit therebeneath, the housing element, of each of said sifting units carrying a substantially horizontal, annular, sifting element pervious to particles not exceeding a predetermined size; but impervious to particles exceeding said predetermined size and adapted to discharge such oversize particles over its outer periphery upon orbital movement of said sifting structure about said axis of gyration, said sifting element of each of said sifting units being spaced inwardly from the housing element thereof to provide a peripheral discharge passage means for particles discharged over the outer periphery of such sifting element, central openings through said ysifting units providing central outlet pasing element of each of said sifting units above vthe lowermost sifting unit in said stack lfurther carrying a downwardly and inwardly ,sloping funnel below the sifting element thereof for conveying particles passing through the sifting element thereof inwardly and downwardly to said central outlet passage means, and the housing element of each of said sifting units above the lowermost sifting unit in said stack additionally carrying a downwardly and inwardly sloping funnel for conveying parti-cles discharged over the louter periphery of the sifting element of such sifting unit into the corresponding peripheral discharge passage means downwardly and inwardly onto the sifting element of the sifting unit therebeneath, the central openings in the funnels last deiined being larger than said central outlet passage means, but smaller than said peripheral discharge passage means; a cover seated on the housing element of the uppermost sifting unit in said stack and providing inlet means for the introduction of particles to be sifted into the uppermost sifting unit in said stack; a base on which the housing element of the lowermost sifting unit in said stack is seated, said base being provided with outlet means communicating with said central outlet passage means and being provided with discharge means communicating with said peripheral discharge passage means; and means for securing said base, said sifting units, and said cover together.

9. In a sifting structure adapted to be gyrated in an orbit about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a stack of annular housing elements substantially symmetrical about said central axis, each of said housing elements above the lowermost housing element in said stack being seated on the housing element therebeneath; a substantially horizontal, annular, sifting element carried by each of said housing elements, each of said sifting elements being concentric with the corresponding housing element and being spaced inwardly therefrom; a funnel carried by each of said housing elements above the lowermost housing element in said stack, said funnels being of substantially the same diameter as said sifting elements and sloping inwardly and downwardly toward central openings in said funnels which register with central openings in the respective sifting elements therebeneath; and another funnel carried by each of said housing elements above the lowermost housing elements in said stack and below the iirst dened funnel carried thereby, said other funnels being of substantially the same diameter as the outer diameter of the annular spaces between said sifting elements and said housing elements and sloping inwardly and downwardly toward central openings therein of a diameter larger than the inner diameter of said sifting elements.

10. In a sifting structure movable in an orbit about a substantially vertical axis of gyration and having a. central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a substantially horizontal, annular, lower, sifting unit substantially symvmetrical about said central axis; and a substantially horizontal, annular upper, sifting unit also substantially symmetricalabout said central axis and seated on said lower sifting unit, said upper sifting unit including a funnel which slopes inwardly and downwardly toward a central opening therein which registers with a central opening in said lower sifting unit, said funnel being vformed `of resilient sheet material and being in a state o'f upward deformation so that it is biased downwardly into positive engagement with said lower sifting unit by its inherent resilience.

11. In a sifting structure movable in an orbit about a substantially vertical axis of gyration and having a central axis which is substantially parallel to but spaced from said axis of gyration, the combination of: a substantially horizontal, annular, lower, sifting unit substantially symmetrical about said centra-l axis; and a substantially horizontal, annular, upper, sifting unit also substantially symmetrical about said central axis and seated on said lower sifting unit, said upper sifting unit including a funnel which slopes inwardly and downwardly toward a central opening therein which registers with a central opening in said lower sifting unit and which is encircled by an annular flange inserted into the central opening in said lower sifting unit, said funnel being formed of resilient sheet material and the vertical distance between its base and its apex when said funnel is in an undeiorined state being greater than the vertical spacing between the central openings in said upper and lower sifting units so that when the annular ange encircling said central opening in said funnel is inserted in said central opening in said lower sifting unit, said funnel is in a state of upward deformation and is therefore biased downwardly into positive engagement with said lower sifting unit by its inherent resilience.

l2. A sifting structure as defined in claim 11 wherein said lower sifting unit includes a collar encircling the central opening therein, said annular ange encircling said central opening in said funnel being telescoped into said collar.

13. A sifting structure according to claim 9 wherein the central opening in each of said sifting elements below the uppermost is dened by a collar, and wherein each of the funnels rst mentioned in claim 10 is seated on the collar dening the central opening in the sifting element therebeneath, each of said first-mentioned funnels being in a state of upward deformation when said housing elements are stacked and being formed of resilient sheet material so that the inherent resilience thereof biases it downwardly into positive engagement with the collar dening the central opening in the sifting element therebeneath.

14. In a gyratory sifter, the combination of: a supporting structure; a sifting structure mounted on said supporting structure for orbital movement about a substantially vertical axis of gyration and having a central axis which is substantially parallel to and spaced from said axis of gyration, said sifting structure including a stack of substantially horizontal, annular sifting units each of which is substantially symmetrical about said central axis, said annular sifting units being provided with aligned central openings therethrough which cooperate to provide an unobstructed, central passage means common to al1 of said sifting units and extending vertically along said central axis through all of said sifting units; and means for producing orbital movement of said sifting structure about said axis of gyration, including a crank-r 19 20 shaft connected to said sifting structure and ex- Number Name Date' tending through said central passage means. 2,020,013 Bailey Nov. 5, 1933 2,098,128 Bailey Nov. 2, 1937 f f. `l-References Cited in the le of this patent 2,295,293 Naeher sept. 22I 1942 UNITED STATES PATENTS 5 FOREIGN PATENTS Number Name Date Number Country Date 595,985 Wolf De. 21, 1897 4,333 Great Britain 1394. 641,986 McAnulty Jan. 23, 1900 23,671 Great Britain 1893 726,172 Korab Apr- 21 1903 10 550,661 Great Britain Jan. 19, 1943 1,351,760 Kallom et al Sept. 7, '1920 

